When naked shell pickers wrap pearls in waters nearly 30 meters deep where sharks often haunt, they occasionally find extremely precious natural black pearls. But this discovery is very rare: every time you open 15000 oysters, you can find a natural pearl. Long before artificial breeding, black pearls had a rare and precious reputation. Royal nobles all over the world like to wear jewelry inlaid with black pearls, which makes it enjoy the reputation of "the queen's pearl" and "the queen among pearls". The most famous of these natural black pearls is Azra, which is the central decoration of a necklace in the jewelry of the Russian Tsar Empire. In ancient China, black pearls symbolized wisdom and were guarded between dragon teeth. He who wants black pearls must conquer the dragon first.